Black Soldier Fly (Hermetia illucens) Larvae and Prepupae Defatted Meals in Diets for Zebrafish (Danio rerio)

SIMPLE SUMMARY: Aquaculture accounts for 52% of the world’s production of fish for human consumption and its growth relies on finding new alternative protein sources to fishmeal to use in aquafeeds. To make fish feed more sustainable, insects have emerged as valuable alternatives due to their high nutritional value. In this context, black soldier fly (BSF) meals have been used to replace, partially or totally, fishmeal in aquafeeds. However, due to relevant nutritional peculiarities of BSF developmental stages, it is crucial to understand how they can affect fish growth performance and health status. In this study, we evaluated the effects of total dietary replacement of fishmeal with defatted BSF larvae and prepupae meals on the growth performance of zebrafish from larva, through adult stages, in a 60-day feeding trial. Moreover, the effects of the two BSF meals on the expression of genes involved in growth, stress- and immune- responses, as well as hydrolysis of chitin were investigated. Overall, our results showed the beneficial role of defatted BSF meals in zebrafish diet, especially regarding prepupae meal, suggesting that black soldier fly meals could totally replace fishmeal without negatively affecting growth and wellness of zebrafish. ABSTRACT: The black soldier fly (BSF) Hermetia illucens is receiving increasing attention as a sustainable fishmeal alternative protein source for aquaculture. To date, no studies have explored the effects of fishmeal replacement with BSF V instar larvae or prepupae meals due to their peculiar nutritional properties on fish performances. This study investigated the effects of 100% replacement of fishmeal (control diet) with defatted BSF meals (V instar larvae and prepupae meals, treatments) on growth performance and welfare of zebrafish (Danio rerio), from larvae to adults, in a 60-day feeding trial. Following the inclusion of BSF meals, the expression of key genes involved in growth (igf1, igf2, mstnb, myod1, myog, myf5), hydrolysis of chitin (chia.2, chia.3, chia.5), immune- (il1b, il6, tnfα), and stress- (hsp70 and nr3c1) responses, as assessed by qPCR, was modulated in all of the molecular pathways, except for the stress response. Overall, our findings showed that both BSF meals can totally replace fishmeal without adverse impacts on adult zebrafish growth parameters (final total and standard length, final body weight, weight gain, daily growth rate, specific growth rate) and welfare, with BSF prepupae meal inducing the most beneficial effects, thus suggesting their potential application to meet fish requirements in aquaculture.